356 BOTANICAL GAZETTE [NOVEMBER 
the apical cell of a filament never divides except to give rise by 
lateral outgrowths to a new branch of the filament. 
MORPHOLOGY AND DEVELOPMENT OF THE 
PROCARPIC BRANCHES. 
The procarps of the genus Ptilota are found in certain spe- 
cialized portions of the frond. called procarpic branches. In P. 
serrata the procarpic branches for the most part take the place of 
the smaller pinnules usually found on sterile plants. They are 
therefore attached to the nodes of the pinne and situated 
opposite well developed pinnules. Procarpic branches are some- 
times to be found on the edge of the pinnules, but they are not 
common in this species. The structure of the procarpic branches 
clearly shows their homology with the smaller pinnules, and their 
development is so similar that it is impossible to distinguish the 
younger stages from one another. Each adult procarpic branch 
contains an axial siphon which consists of from nine to twelve 
(typically ten) segments. Pairs of short lateral filaments arise 
from the segments in the same manner as in ordinary pinnules, 
and as the branch grows older a rather insignificant system of 
corticating filaments is developed. Several early stages of pro- 
carpic branches are shown in jig. f,. the ces being shaded. 
Those attached to the 1, 111, and 1v nodes consist of but a single 
cell. Later stages are shown attached to nodes V, VI, and Vil. 
A typical adult procarpic branch is illustrated by fig: 3: ne 
specimen from which the figure was drawn being situated on the 
twelfth node of a pinna. 
When procarpic branches are found on the pinnules they ct 
seen to take the place of the teeth that usually occur along : “i 
edge of these structures, and to be continuations of the late 
branches from the axial siphon of the pinnules. 
The extremity of the adult procarpic branch has t 
structure whether the latter is situated on a pinna or 
There is always a terminal cell, the former apical ae ue oa 
3, cell 11), and it is from this that the group of por ae ms 
derived. The apical cell and all structures derived from it ar | 
he same 
pinnule. 
